Mayor Bloomberg scored a mayoral endorsement coup yesterday, winning the support of the New York Building and Construction Trades Council, a body that represents 60 affiliated unions and 100,000 members in the five boroughs. The union endorsed Mr. Bloomberg’s opponent, Mark Green, in the 2001 election.

“Our 100,000 union members want the same thing all New Yorkers want: good jobs, safe streets, and better schools,” the labor group’s president, Edward Malloy, told a raucous crowd at downtown Brooklyn. “The other candidates don’t seem to have the vision. The only vision they say is that everything that Michael Bloomberg is doing is not right.”

Mr. Bloomberg, for his part, told the group he was proud to stand among them and vowed to “be scrupulously honest” and to “work as hard as I can.”

Analysts said they expect yesterday’s union nod to be the first in a roster of announcements from organized labor, thanks to Mr. Bloomberg’s championing of a new West Side stadium for the New York Jets football team.

While the conventional wisdom has been that Mr. Bloomberg’s decision to associate himself so closely with the project would become a millstone for his re-election campaign, it seems to have had the opposite effect with private-sector unions.

“People just don’t get how important the stadium is to the building trades,” a political consultant, Scott Levenson, the president of the Advance Group, said. “It is the biggest jobs program for them in a generation.”

Mr. Bloomberg has presented the project as a job-creation program for the city. To hear him tell it, the $2.2 billion stadium will generate about 18,000 construction jobs, or an average of 4,500 jobs, during the four years of construction.

Those kinds of numbers have helped him woo a roster of construction-affiliated unions. The Steamfitters Local 638, Engineers Local 15, cement and concrete workers, plumbers, painters, and carpenters have all backed the project.

A political science professor at Baruch College, Douglas Muzzio, said: “He sold the stadium not just for the Olympics but as a jobs program, so labor-union endorsements should not be unexpected. You reward people with jobs, and they will reward you. That’s how this works.”

More broadly, Mr. Bloomberg is taking credit for the city’s economy having added new jobs in 20 consecutive months, and for a decline in its unemployment rate to the national average for the first time in 17 years.

If the economic numbers stay steady and more unions line up behind the mayor, Mr. Levenson said, the Bloomberg campaign will be able to blunt the one attack that opponents have been able to make stick: that the billionaire businessman is out of touch with the average New Yorker.

“The union support inoculates him from those negatives,” he said. “And it creates a different dynamic in which he is on the side of average New Yorkers and working families. That is going to end up really helping him.”